The term Black Swan is certainly over-used. We did a study a couple of years ago on 50 major process safety events over a 25 year span. Of those, none were black swans… but, some in the industry (some managers & process safety speakers) referred to them as black swans… “how could we have known?”
In these 50, the companies either 1) did not maintain the independent protection layers they knew they needed and/or did not maintain the primary containment shell (and they knew how to do this) or 2) there were barriers missing for accident scenarios that were unique to startup, shutdown, or online maintenance modes of operation, yet the organization had ignored requirements to perform a process hazard analysis of the deviations from steps of procedures that govern those modes of operation.
With that said, I have seen a few authentic black swan events; related to mysteries in the chemistry that had not been. Less than 1% of the major accidents are do the Back Swan events; let’s focus the 99% instead that are knowable and preventable; then when we conquer those, we can turn our focus to Black Swans… otherwise it is as if we are chasing Wild Geese (and accomplish nothing significant).